Backyard Bug Bonanza

None needed.

Pick two different locations in your neighborhood where you think you might find insects, such as a sports field, a garden, or a bushy hedge. As you walk through the first location, sweep the net through 10 times. Then use your hands to close the top of the net to trap what you’ve caught. If a bee or wasp ends up in the net, set the net down and allow it to escape before continuing.

When you’re done, survey the insects you’ve caught by slowly opening the net, bit by bit, recording the different types as they’re revealed. You don’t need to identify them by species or name—a simple qualitative description that allows you to distinguish between varieties will suffice (for example, “tiny black fly”).

As you work, be sure to keep one hand around the opening of the net to prevent the rest of the insects from escaping. If you’re uncomfortable holding onto the net while collecting data, you might want to transfer its contents into a large, clear plastic bag for analysis. This is also helpful if you find that your local insect varieties tend to fly or jump out of the net quickly.

Once data collection is complete, invert the plastic bag to return the insects to their habitat. Empty plant debris from the net before heading to the second location, and repeat the same procedure there.

Which area resulted in a longer list of insect varieties? Why do you think that is?

Biodiversity—the variety of living things found on Earth—can be measured at different scales: within a species (genetic variation), between species (the focus of this Snack), and between ecosystems. Environments that contain many different species are said to have high biodiversity, while environments that contain few varieties of species are said to have low biodiversity. When one part of a habitat (such as an area’s plant life) is highly diverse, the rest of the organisms in the habitat (such as that area’s insects) will also show greater diversity.

Different insect species can occupy and fill different niches within the same area. A niche is the physical environment to which an organism is best adapted, or the role that organism plays within the location. For example, a species that depends on the leafy part of a plant for its best source of food occupies a different niche from a species that relies on the nectar from the plant’s flowers. That’s why you may see a greater diversity of insects in areas such as vegetable gardens and creek banks, where many different niches can be filled, each providing the specific resources preferred by a different insect species.

Areas with monocultures, on the other hand, such as lawns and cornfields, tend to have fewer varieties of insects because they offer so few niches. When one species inhabits a grassy lawn, for example, it can easily overtake the whole area, taking advantage of a sustained food supply that’s all in one place. The result is an area that’s high in biomass, but low in biodiversity. A more diverse area results in a more diverse community of insects.

Try to vary aspects of your data collection. For example, how might the weather or the time of day affect your results? How about areas in the shade or in the sun?

Note that this Snack can also serve as a starting point for a discussion of the consequences of modern agricultural practices. Human-made monocultures, such as corn and wheat fields, make harvesting more efficient, but often require the use of insecticides to keep insect populations from damaging plants and reducing crop yields. This discussion could extend to the challenges of low genetic diversity, the overuse of pesticides, and the development of genetically modified organisms.

Before beginning this activity, students may need to be briefed on how insects are different from other arthropods, such as arachnids or worms. It may also be helpful to discuss the difference between biomass (the total mass of organisms in an area) and biodiversity (the variety of organisms found in an area). Finding hundreds of tiny black flies in one area, for instance, means you’ve found high biomass, but low biodiversity.

This Snack works better at certain times of the year and can be impacted by weather events, such as drought or storms. This could give students an opportunity to do a long-term study of how biodiversity changes over time. If a long-term project is beyond the scope of your class and you’ll only do this once, then springtime often gives the best results.

Pollan, Michael. The Botany of Desire: A Plant’s-Eye View of the World. Random House, 2001, Chapter 4 (“The Potato”) contains good background information regarding monocultures and the consequences of trying to control nature.